RU2632298C2 - Method for fibrous blank manufacturing - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method for manufacturing a fibrous blank by laying bundles of reinforcing fibers on a surface and/or bundles of reinforcing fibers layed on surface includes a stage for supplying endless reinforcing fiber bundle in the form of ribbon-shaped tow and provided with a binder from a feeder to a laying head, and said ribbon-shaped tow having tow width of at least 5 mm and binder concentration in the range of 2 to 70 wt % relative to the weight of the ribbon-shaped tow. Spreading of the endless ribbon-shaped tow in a spreading unit located on the laying head and transporting the tow to the transportation direction by means of a first transportation device arranged on the laying head to a longitudinal separation device located on the laying head. When the tow is stabilised in a direction transverse to the transportation direction, the tow is cut in the longitudinal separation device along its longitudinal extension by means of a dividing element into two or more pieces of the tow. Transportation of the tow pieces in the transportation direction by means of a second transport device located on the laying head to the transverse separation unit located on the laying head. The tow pieces are cut by means of a lateral separation unit into bundles of reinforcing fibers of a certain length. The bundles of reinforcing fibers are stacked on the surface and/or on bundles of reinforcing fibers laid on the surface and secured to form the fibrous blank. At that, a relative movement for laying is set between the laying head and the surface.

EFFECT: increase of fiber volume fraction in fibrous blanks.

18 cl, 3 dwg

Description

The invention relates to a method for manufacturing a fiber preform by laying bundles of reinforcing fibers on a surface and / or on bundles of reinforcing fibers laid on a surface. The invention also relates to a method for manufacturing a structural member from a fibrous composite material using a fibrous preform thus manufactured.

In particular, in the field of aviation and space industry, as well as, for example, in the field of mechanical engineering or in the automotive industry, structural elements from fiber composite materials are increasingly used. Fibrous composite materials, in comparison with metal, often have the advantage of lower weight and / or higher strengths. The volume fraction of the reinforcing fibers and, in particular, also the orientation of the reinforcing fibers have a decisive influence on the load capacity of structural elements, especially with regard to their stiffness and their strength. However, this kind of highly loaded material and structural elements must still have the possibility of optimal manufacturing cost in order to be economically attractive.

For the manufacture of such structural elements from a composite material in an intermediate stage, first the so-called fibrous preforms (“preforms”) are made from reinforcing fibers. In this case, we are talking about textile semi-finished products in the form of two- or three-dimensional formations of reinforcing fibers, while the shape may already practically correspond to the shape of the final structural element. In embodiments of such fibrous preforms, which essentially consist only of reinforcing fibers and which still have at least a substantial absence of the matrix component required for the manufacture of structural elements, in the next steps, by infusion or injection into the fibrous preform, also using vacuum, proper matrix material is introduced. Then the curing of the matrix material, as a rule, at elevated temperatures and pressures, with the receipt of the finished structural element. In this case, the known methods of infusion or injection of matrix material are the so-called Liquid Molding (LM method) - liquid filling - or related methods, such as, for example, Resin Transfer Molding (RTM) - transfer molding,Vakuum Assisted Resin Transfer Molding (VARTM) - transfer molding for vacuum Resin Film Infusion (RFI)-impregnation with film binders; Liquid Resin Infusion (LRI) - impregnation with liquid resin - or Resin Infusion Flexible Tooling (RIFT) - impregnation with resin using a membrane. The fibrous material used for the manufacture of fibrous preforms can also be pre-impregnated, for example, with small amounts of polymeric material, i.e. a binder material to improve the fixation of the reinforcing fibers in the fiber preform. Such pre-impregnated threads are described, for example, in WO 2005/095080.

Methods are also known in which structural elements from a composite material are made from fiber preforms that already have a matrix material content sufficient for a structural element from a composite material. In these cases, these fibrous preforms, for example, in the form using elevated pressure and / or elevated temperature, can be directly pressed to obtain a structural element. Alternatively, instead of applying the mold, it is also possible to use a vacuum bag into which the fiber preform is inserted, and after applying the vacuum and, as a rule, is pressed at elevated temperature to obtain a structural element. A sufficient content of the matrix material for the structural element can be achieved, for example, when the fiber preform is made from bundles of reinforcing fibers that were made from prepregs with the corresponding matrix content. Alternatively, when laying, for example, bundles of reinforcing fibers to form a fiber preform, additional matrix material may, for example, be sprayed during laying.

For the manufacture of fiber preforms from reinforcing fiber bundles, automated processes are often used in which the fiber bundles are laid on or, respectively, in appropriate forms by means of controlled laying heads or devices for laying fibers, while laying can also be carried out by spraying fiber bundles onto or respectively forms. As a rule, in this case, an endless thread of reinforcing fibers is fed to the laying heads, which is then transversely divided into the desired length of the bundle in the laying head or, accordingly, in the apparatus for laying the fibers by means of appropriate cutting devices. Such laying heads equipped with a transverse separation device for fiber tows are described, for example, in WO 2011/045171 or US-A 3011257.

Fibrous preforms can, for example, be made in such a way that short-cut reinforcing fibers, together with a binder, are sprayed onto an adapted to the desired fiber preform configuration, the breathable screen is dispersed, and when vacuum is applied, they are kept on the screen until after the binder has cooled, sufficient workpiece stability. Such a method is described, for example, in WO 98/22644. In the method of WO 98/22644, reinforcing fibers, preferably in the form of short cut fibers, are arranged in a random, isotropic order and orientation. In accordance with examples WO 98/22644, volume fractions of fibers are achieved only up to about 15 vol%, and due to the low volume fractions of fibers, only relatively small strengths of structural elements with respect to thickness are achieved.

In order to achieve higher fiber volume fractions in the preforms or structural elements made from them, it is preferable in accordance with embodiments WO 2012/072405 to lay shortly cut fibers in the form of bundles of reinforcing fibers, these fiber bundles preferably having a length ranging from 10 up to 50 mm. In addition, from the point of view of the highest possible volumetric fractions of fibers and at the same time achievable mechanical properties, it is preferable if the bundles have the smallest possible number of filaments of reinforcing fibers, with an amount of from 1000 to 3000 filaments being particularly preferred. Thus, an almost isotropic material arises that has practically isotropic mechanical properties in the directions of its length. At the same time, due to relatively small dimensions of the beam, this material does not have or has only small areas with an increased proportion of resin and at the same time a reduced proportion of reinforcing fibers, which can lead to weak spots in the structural element. It is easy to understand that the use of bundles of reinforcing fibers having such low titers, i.e. such low amounts of filaments, leads to increased costs, in particular also due to the use of relatively expensive starting materials. But on the other hand, the use of bundles of fibers having rough titers, i.e. fiber bundles having a large number of filaments of reinforcing fibers, although it is more expensive, however, as indicated, the realization of high volume fractions of fibers is impossible or only possible with difficulty.

Therefore, there is a need for an automated method for manufacturing a fiber preform, by which it is possible to produce fiber preforms at a cost-effective manner when high fiber volumes are achieved in the fiber preforms or structural elements made of composite material made accordingly.

Therefore, it is an object of the present invention to provide such a method for manufacturing a fiber preform.

The problem proposed by the invention is solved by a method for manufacturing a fiber preform by laying bundles of reinforcing fibers on the surface and / or on bundles of reinforcing fibers laid on the surface, this method comprising the steps of:

- the supply of at least one endless ribbon-shaped tow of reinforcing fibers provided with a binder, and this at least one tow has a tow width of at least 5 mm and a binder concentration in the range of 2 to 70 weight. % relative to the weight of the ribbon-shaped tow;

- straightening said at least one endless ribbon-shaped tow in a spacer assembly located on the stacking head and transporting said at least one tow in the transport direction by means of the first transport device located on the stacking head to the longitudinal separation device located on the stacking head;

- while stabilizing the specified at least one tow in a direction transverse to the direction of transportation;

- cutting said at least one tow in a longitudinal separation device along its longitudinal extent by means of at least one dividing element into two or more parts of the tow;

- transportation of the tow parts by means of a second conveying device located on the stacking head to a transverse separation unit located on the stacking head;

- cutting the parts of the bundle by means of a transverse separation unit into bundles of reinforcing fibers of a certain length; and

- laying the bundles of reinforcing fibers on the surface and / or on the bundles of reinforcing fibers laid on the surface and fixing the bundles of reinforcing fibers on the surface and / or on the bundles of reinforcing fibers laid on the surface to form a fiber preform, while a relative movement is established between the laying head and the surface for laying bundles of reinforcing fibers on the surface, taking into account the load.

By means of the method proposed by the invention, the production of fibrous preforms from bundles of reinforcing fibers, i.e. from bundles of reinforcing fibers with a low number of filaments of reinforcing fibers during the implementation of high volume fractions of fibers in a fiber preform or, accordingly, made from it a structural element of a fibrous composite material. At the same time, endless ribbon-shaped strands can be used as the starting material, for example, in the form of cost-effective bundles with coarse titers of threads made from reinforcing fibers. Such coarse-titled filaments of reinforcing fibers by means of a longitudinal separation device can first be divided into several parts of the bundle along the length of the filament constituent filaments of the reinforcing filaments, and then the individual parts of the bundle have a lower number of filaments compared to the original filament.

As the reinforcing fibers used in the method according to the invention which form the at least one ribbon-shaped strand, preferably carbon, glass or aramid fibers or mixtures of these fibers with each other or with thermoplastic fibers are used. Particularly preferred are carbon fibers.

In one preferred embodiment, said at least one endless ribbon-shaped tow of reinforcing fibers provided with a binder is a filament yarn having at least 12,000 filaments that is flattened in the shape of a ribbon. Especially preferred are filaments of this kind having filaments ranging from 24,000 to 50,000. In the case where the ribbon-shaped strand of reinforcing fibers provided with a binder is a filament, the concentration of binder in one of the preferred embodiments is in the range of 2 up to 14 weight. %, and in one of the particularly preferred embodiments in the range from 3 to 7 weight. % relative to the total weight of the binder filament.

Then, the binder can be a fiber impregnation composition, which is usually applied to the filaments of the filament yarn to achieve better processability and good adhesion of the fibers, i.e. at least partially connecting filaments to each other. Such impregnation formulations are often based on epoxy resins. However, the inventive method requires a content that is higher than the commonly used concentration of the impregnation composition, which, as indicated, preferably lies in the range from 2 to 14 weight. % and particularly preferably in the range from 3 to 7 weight. % relative to the total weight of the binder filament.

In this case, thermoplastic or uncured or partially cured thermosetting polymers or compositions of these polymers are possible as binders. Suitable thermosetting polymers are, for example, polyethyleneimine, polyetherketone, polyether ether ketone, polyphenylene sulfide, polysulfone, polyethersulfone, polyethersulfone, aromatic polyhydroxyether, thermoplastic polyurethane resins or mixtures of these polymers. As uncured or partially cured thermosetting polymers, for example, epoxides, isocyanates, phenolic resins or unsaturated polyesters are possible. Moreover, it is preferable if the endless, ribbon-shaped strand of reinforcing fibers provided with a binder is a filament, which at the processing temperature in the region of the laying head, i.e., as a rule, is not sticky at room temperature and, for example, can unwind from a reel. However, at elevated temperatures, a binder or, respectively, reinforcing fibers provided with a binder should be sticky and contribute to good adhesion of the fiber bundles made from them. Such threads of reinforcing fibers or, respectively, strands of reinforcing fibers are described, for example, in WO 2005/095080, the description of which is hereby referred to directly. The filament yarns described there are infiltrated by a binder consisting of several different epoxy resins, and these epoxy resins in a certain way differ from each other in their properties, such as epoxy number and molecular weight, as well as their concentration.

In one preferred embodiment of the method of the invention, said at least one strand is a pre-impregnated filament, and the binder consists of a composition of the first and second resin, wherein the filament of the filament is impregnated with the first resin composition and, at least, of the first resin composition partially connected, and this composition of the first resin contains at least two bisphenol A epichlorohydrin-resins H1 and H2 in a weight ratio of H1: H2 from 1.1 to 1.4, while H1 has an epoxy number of 1850 to 2400 mmol / kg, an average molecular weight M _N of 800 to 1000 g / mol and is solid at room temperature, and H2 has an epoxy number of 5000 to 5600 mmol / kg, an average molecular weight of M _N < 700 g / mol and is liquid at room temperature, and also contains an aromatic polyhydroxy ester P1, which has an acid number of 40 to 55 mg KOH / g and an average molecular weight M _N of 4000 to 5000 g / mol, and the pre-impregnated filament yarn has a second resin composition on its outside particles or droplets to the filaments, moreover, this second resin composition is solid at room temperature, has a melting point in the range from 80 to 150 ° C, and is present on the outside of the yarn in a concentration of from 0.5 to 10 weight. % relative to the total weight of the pre-impregnated filament yarn, and at least 50% of the outer side of the yarn is free from the composition of the second resin, and inside the yarn is free from the composition of the second resin. Such filament yarns previously impregnated with a binder are described in patent application WO 2013/017434, the corresponding description of which is hereby incorporated by reference.

In another preferred embodiment, said at least one strand may preferably be a prepreg of reinforcing fibers unidirectionally arranged in the direction of extension of the prepreg and at the same time in the direction of transport of the prepreg. In the context of the present invention, a prepreg is understood to be a semifinished product of reinforcing fibers impregnated with a polymer matrix system. In this case, we can talk about the prepreg of the thread ("tow prepreg"), i.e. about a single thread impregnated with a matrix system. However, we can also talk about a semi-finished product in the form of a web, which consists of adjacent reinforcing fibers located parallel to each other and unidirectionally oriented, impregnated with a matrix system. In the case of prepregs, the matrix system is then the binder.

Thermoplastic polymers or uncured or partially cured thermosetting polymers or polymer compositions are also possible as a matrix system or, respectively, a binder in these cases, and the polymers mentioned above can be referred to. In the case where said at least one strand of reinforcing fibers provided with a binder is a prepreg, preferably when the binder, i.e. the matrix system is available in concentrations ranging from 15 to 70 weight. % relative to the weight of the prepreg, and in the case when the reinforcing fibers are carbon fibers, particularly preferably in the range from 20 to 60 weight. %

The specified at least one ribbon-shaped bundle of reinforcing fibers provided with a binder can be unwound from a reel or, in the case of using a prepreg, from a roll as a feeder and fed to the laying head. Preferably, a feeder, i.e. a coil or a roll is fixedly connected to the stacking head, so that when moving the stacking head, the feeder is driven with it. In this way, a stable course of said at least one tow may be achieved.

To improve the reliable positioning of said at least one ribbon-shaped tow, to increase its width and to achieve a good longitudinal separation device, said at least one tow is guided through a spacer assembly located on the stacking head, which, when viewed in the direction of transport at least one endless ribbon-shaped tow through the stacking head is located in front of the first transport device. One separate system or a system of several stationary and / or rotatably supported rods is suitable as a spacer assembly, by means of which the tension of the threads in the bundle can be increased. The surface of the rods should preferably have such properties that the abrasion of the strands of thread guided along it is low. To do this, you can resort to known surfaces or materials. The rods are preferably arranged so that the at least one endless ribbon-shaped strand is guided around the rods with a twisting angle greater than 20 °.

Preferably, said at least one tow of reinforcing fibers provided with a binder has a tow width of at least 6 mm. It is also preferred that said at least one tow has a ratio of its width to its thickness of at least 20.

After the straightening unit, said at least one bundle passes through a first conveying device, by means of which a certain transportation speed of said at least one bundle is established, and by means of which said at least one bundle is supplied to a longitudinal separation device.

Said at least one tow is stabilized by means of suitable devices for laterally directing said at least one tow of reinforcing fibers in a direction transverse to the transport direction, so that it is guided directly and without lateral deviations through separate transport and separation devices. Due to this, a clean cut with clean cut edges can be achieved in the longitudinal separation device, since the cut can be carried out at least almost parallel to the filaments of the specified at least one bundle. Preferably, rods, rollers, rollers or other guiding devices, as well as, if necessary, transporting devices are oriented at right angles to the direction of transportation of said at least one ribbon-shaped bundle, and also parallel to each other. In addition, in one preferred embodiment, the rods, rollers, rollers, or other guiding elements by which said at least one ribbon-shaped bundle is guided can be barrel-shaped at respective points of contact with the bundle. Preferably, the contour of the guide elements in the barrel-shaped region has a radius in the range of 50 to 600 mm.

For a longitudinal and transverse cutting process (transverse separation process), it is preferable if said at least one strand of reinforcing fibers with tension is guided through the stacking device and, in particular, tension increases in said at least one reinforcing strand between the first and second conveying device fibers. Due to this, reliable maintenance of a planar state and good expansion of said at least one strand of reinforcing fibers can be achieved, as well as a stable course of said at least one strand of reinforcing fibers, which, in particular, contributes to a good cutting result in a longitudinal separation device. This can be achieved, for example, by setting the speeds of the first and second conveying device so that the speed of the second conveying device is higher than the speed of the first conveying device. Preferably, said at least one tow is connected to a longitudinal separation device with a pull force of 40 to 300 cN per mm of tow width.

The first and / or second conveying device, which is passed by the at least one rope, in one of the preferred embodiments consists of one or more drive rollers or rollers by means of which the at least one rope is transported. In this case, the rollers or, respectively, the rollers can be arranged relative to each other so that, when used, the indicated at least one strand of reinforcing fibers encircles these rollers or, respectively, the rollers. In another preferred embodiment, the first and / or second conveying device includes a driven and speed-controlled pair of rollers having an adjustable clearance between the rollers of the pair of rollers, through which at least one reinforcing fiber bundle is transported due to the pressure created by the pair of rollers .

In addition, in one also preferred embodiment, the first and / or second conveying device may include an injection device through which said at least one endless ribbon-shaped strand of reinforcing fibers is conveyed. In this case, the discharge device is connected with an adjustable air supply.

By means of a longitudinal separation device, said at least one bundle is cut along its longitudinal extent into parts of the bundle. The thus obtained parts of the tow are preferably in the range of 0.5 to 5 mm and particularly preferably in the range of 0.5 to 3 mm. With fiber bundles made from such parts of the bundle, high volume fractions of fibers in the fiber preform or structural elements made of fiber composite material respectively made from it can be achieved.

The longitudinal separation device includes at least one separation element for separating said at least one strand of reinforcing fibers along its longitudinal extent. The specified at least one separation element of the longitudinal separation device may be a laser beam, air-jet or water-jet system or a mechanical separation element, for example, in the form of at least one fixed element, for example, a fixed knife, or at least one a rotating separation disc, which is preferably provided with a drive. In this case, the drive can be adjustable and designed so that a speed difference can be established between the peripheral speed of the at least one spacer disk and the transport speed of the at least one reinforcing fiber bundle passing through the longitudinal separation device. The direction of rotation of said at least one rotating spacer disk may be in the direction of transportation of said at least one ribbon-shaped bundle or opposite thereof. In the method of the invention, it turned out to be preferable if the peripheral speed of said at least one separation disk can be set 2-15% higher than the transportation speed of said at least one rope passing through the longitudinal separation device. Particularly preferred is the peripheral speed of said at least one spacer disc, which is 4-10% higher than the transport speed of said at least one tow.

In one preferred embodiment, in the case where said at least one separating element is a mechanical separating element, said at least one strand and said at least one separating element are pressed against a certain force with a certain force. In this case, for example, the rotating separation disk can be connected to a force-controlled clamp, by which the rotating separation disk is pressed with a certain force to the at least one strand of reinforcing fibers that is shared along its longitudinal extent. Preferably, said at least one harness is pressed against said at least one mechanical separation member. By such a clamp, when used in cases where the at least one strand of reinforcing fibers has a twist, for example, twisting of a thread in the case when this bundle is a thread, the separation of the bundle in the twisting region across to the direction of the fibers is prevented. Already partial separation of the bundle transverse to the direction of the fibers can lead to breakage of the bundle and, as a result, to interrupt the cutting process and at the same time laying.

In one preferred embodiment of the method, said at least one bundle of reinforcing fibers provided with a binder can be cut in a longitudinal separation device into more than two parts of the bundle. Thus, the number of filaments in individual parts of the bundle can be reduced so that bundles of fibers with a sufficiently small width are obtained. The use of such bundles of fibers with a smaller width allows, in turn, to realize high volume fractions of filaments in the fiber preform made with their help or, respectively, in the resulting structural element made of composite material. The number of dividing elements of the longitudinal separation device is oriented to the number of harness parts to be obtained.

Also, one of the preferred embodiments is when said at least one bundle is cut into pieces of a bundle of different widths. That is, said at least one dividing element can be positioned relative to the devices for laterally guiding said at least one endless ribbon-shaped strand of reinforcing fibers so that said at least one bundle is divided into parts of the bundle in the center or eccentrically. Also, in the case of one separate strand of reinforcing fibers, which must be divided into three or more parts of the bundle, these several separating elements can be located relative to each other and / or relative to the devices for lateral direction so that the resulting parts of the bundle of different widths.

In one preferred embodiment of the method of the invention, several endless ribbon-shaped strands of reinforcing fibers provided with a binder are fed and fed to the stacking head or, accordingly, devices located on it, such as, in particular, a longitudinal separation device and a transverse separation unit . In this case, the bundles can be the same or different lengths. For example, all of these several tows may be carbon fiber tows. However, carbon fiber tows can also be combined, for example, with fiberglass tows.

Then, in the case of supplying several bundles of reinforcing fibers equipped with a binder to the laying head, there are several feeders, for example, in the form of creel, and the corresponding number of devices for the lateral direction of individual bundles. Moreover, these several harnesses are guided so that they are located next to each other, while individual harnesses can be removed from each other, or they can lie touching each other. Then, the longitudinal separation device includes several separation elements, the number of which is based on the number of parts of the tow, which should be made of adjacent to each other several strands of reinforcing fibers. For example, a longitudinal separation device has four dividing elements, when two adjacent to each other, having the form of ribbons of a string of strands from a thread must be cut each into three parts of a bundle.

In another preferred embodiment, in the presence of several endless ribbon-shaped strands of reinforcing fibers provided with a binder, i.e. several bundles of reinforcing fibers, by means of appropriate guiding devices using the first transport device, they can be fed into the longitudinal separation device so that they are located one above the other, i.e. lay on top of each other. In this case, the ribbon-shaped strands are cut together in the longitudinal direction by the same dividing elements. For example, in the case where two ribbon-shaped strands of thread should be cut each into three parts of the bundle, the longitudinal separation device has two separation elements.

After cutting said at least one reinforcing fiber tow into parts of the tow, these parts of the tow through the second conveying device are led to the transverse separation unit. Then, by means of the transverse separation unit, the parts of the bundle obtained in the longitudinal separation device are cut into bundles of fibers of a certain length transverse to the direction of their length, i.e. a predetermined length, while the length of the resulting fiber bundles depends on the frequency with which the cuts are made across to the length direction of the parts of the bundle depending on the speed of transportation, i.e. from the frequency of transverse cutting. In one of the preferred embodiments, the transverse separation unit is connected to the transport devices so that when the transportation speed changes, the cross-cutting frequency changes so that the length of the resulting bundles of reinforcing fibers remains constant. In another preferred embodiment, the cross-cutting frequency can be set independently of the transport speed, so that at a constant transport speed, bundles of reinforcing fibers of different lengths can be produced. Of course, a combination of installation possibilities is also included in the invention, in which, on the one hand, the transport speed serves as a control value for the cross-cutting frequency, however, at a set transport speed, the cross-cutting frequency may vary. Due to this, the length of the fiber bundles during the implementation of the method of the invention can vary and, for example, adapt to the features of the contour of the manufactured fiber preform. Therefore, in one of the preferred embodiments, the cross-cutting frequency varies with time varying the length of the fiber bundles. Preferably, the harness portions are cut through a transverse separation unit so that the resulting fiber bundles have a length in the range of 10 to 100 mm. Particularly preferred is a fiber bundle length in the range of 10 to 75 mm.

With respect to the transverse separation unit, one can resort to known aggregates and methods of cutting reinforcing fibers transverse to the direction of their length. As such units, for example, units for water- or air-jet cutting of fibers, for cutting fibers by means of laser beams, units having, for example, pneumatically advanced jack-off knives transverse to the transport direction, rotary transverse cutters having a knife roller and counter roller, or rotary knives, the axis of rotation of which extends in the direction of transportation of the parts of the tow or at an angle of up to 60 °, preferably up to 20 ° to them. The latest rotary knives are described, for example, in DE 202010017556 U1 or EP-A-3351880 A1. In one preferred embodiment, the parts of the tow are transversely separated by a rotary transverse cutter, in which the knives are pressed against the cut at least one strand of reinforcing fibers without creating significant back pressure on the other side of the tow. This method with brittle reinforcing fibers, such as, for example, carbon fibers or glass fibers, leads to brittle fracture at the load site and, at the same time, to a pure transverse separation of the bundle of reinforcing fibers. Such aggregates are described, for example, in EP-A-1144738, EP-A-1394295, EP-A-1723272 or WO 02/055770, the corresponding contents of the description of which are directly referred to.

In one preferred embodiment, the obtained fiber bundles are withdrawn from the transverse separation device by means of a fiber bundle removal device. This can be done, for example, by means of a short conveyor belt. Particularly preferably, the fiber bundles are diverted from the transverse separation unit through the nozzle channel of the nozzle head into which compressed air is supplied. Preferably, a venturi nozzle is arranged in the nozzle channel of the nozzle head for introducing compressed air into the nozzle channel. Due to this, the fiber bundles for the manufacture of a fiber preform with increased speed can be carried to the surface and / or to the fiber bundles laid on the surface, i.e. get dusty.

The nozzle head for removing fiber bundles may have means for introducing matrix material into the nozzle channel. In one of the preferred embodiments of the method with their help, the matrix material in the form of particles can be introduced into the nozzle channel, carried out together with transversely separated bundles of fibers and carried out or respectively sprayed onto the surface and / or onto bundles of fibers laid on the surface. The means for introducing the matrix material can, for example, be a Venturi nozzle which extends into the nozzle channel and through which matrix particles are introduced into the nozzle channel. However, it can also be a spray nozzle located in the nozzle channel, by means of which liquid matrix material is injected. The filing of the matrix material may be preferable so that when laying the fiber bundles made by the laying device on the surface using the matrix material, they contribute to better adhesion to each other and, at the same time, better fixation of the fiber bundles between themselves and on the surface. At the same time, the matrix material in the amount required for the manufacture of a structural element from a composite material can, for example, be supplied already in the manufacture of a fibrous preform.

When performing the method of the invention with respect to better adhesion to each other and, at the same time, better fixation of the fiber bundles between themselves and on the surface, it may be preferable if the fiber bundles and, if necessary, matrix material supplied in the form of particles or droplets after the transverse separation unit and before laying or when laid on the surface and / or on the bundles of reinforcing fibers laid on the surface, they are heated. In this case, the binder with which the fiber bundles are provided and / or the matrix material can be activated, i.e. become sticky, for example, in such a way that the fiber bundles are heated to a temperature above the melting point of the binder. Heating can be carried out, for example, by blowing with hot air or by means of heated ambient air, by laser radiation or by means of infrared radiation. After the fiber bundles hit the surface of the manufactured fiber preform and after cooling, the fiber bundles are fixed again by the binder that has hardened after this.

According to another preferred embodiment of the method, the matrix material in the form of particles or droplets can also be separate from the fiber bundles, however, simultaneously with them, they are sprayed onto the surface and / or on the bundles of reinforcing fibers laid on the surface. This can be done, for example, by directed spraying of such particles or droplets by means of a heat source, such as, for example, a flame or a microwave or infrared field. Preferred here is a thermal spraying method, which is described, for example, in WO 98/22644 or in US 2009/0014119 A1.

Depending on the binder provided with said at least one reinforcing fiber tow, the matrix materials supplied if necessary, and the temperatures prevailing during the stacking of the fiber bundles, the cooling step following the laying of the fiber bundles is preferable to stabilize the fiber preform.

In accordance with the invention of the method, the bundles of reinforcing fibers are laid on the surface and / or on the bundles of reinforcing fibers laid on the surface and fixed on the surface and / or on the bundles of reinforcing fibers laid on the surface to form a fibrous preform. Preferably, a surface, i.e. The laying surface already has a certain contour that is adapted to the contour of the manufactured fiber preform or, respectively, of the structural element made of the fibrous composite material made from it.

The laying surface or surface may be a screen having openings on which fiber bundles are laid, if necessary with the simultaneous addition of matrix material, or on which they are sprayed. In the case of the use of such a screen, the fixation of the fiber bundles can be maintained at least by the fact that a vacuum is applied to the side of the screen, turned away from the side of the screen on which the fiber bundles are stacked. In this way, air is drawn in through the screen, whereby fixation of the fiber bundles can be achieved. The surface may also be provided with adhesive or matrix material previously applied and adhesive during installation, so that it contributes to good adhesion of the fiber bundles. Adhesion can also occur while matrix material is added together with fiber bundles using this matrix material.

For the manufacture of structural elements from a fibrous composite material having high volume fractions of fibers, it is preferable if, in the method according to the invention, the step of laying bundles of reinforcing fibers is followed by a compacting step in which the stacked bundles of reinforcing fibers are compacted to achieve a high volume fraction of fibers. This compacting step can be performed so that the preform obtained after laying the fiber bundles in a mold, preferably at an elevated temperature, is subjected to increased pressure, for example, in a press. Also, the preform obtained after laying the fiber bundles can be placed in a vacuum bag, and then compacted with a vacuum and at elevated temperature.

In one preferred embodiment of the method for manufacturing a fiber preform, the stacking head is connected to a controlled positioning unit by which the stacking head moves relative to the surface. In one embodiment, the stacking head can be connected via a robot with an articulated arm located on the base of the machine, and by means of this robot with an articulated arm and held by a robot with an articulated arm of the robot joint, can be positioned in at least two axes relative to the surface. In another embodiment, the stacking head may be secured by a hinge head in the portal rack and be able to position at least around two axes relative to the surface. Preferably, the stacking head is capable of positioning at least 6, and particularly preferably around at least 9 axes.

In another embodiment, the surface on which the fiber bundles are laid is stationary, and the relative movement between the laying head and the surface is due to the movement or, accordingly, the positioning of the laying head. Alternatively, the surface on which the bundles of fibers are laid can move, for example, by means of a robot with an articulated arm, and the laying head can be fixed. Of course, mixed variants of the present method are also included, in which, for example, the surface moves by means of a robot with an articulated arm around, for example, 6 axes, and the laying head is also capable of positioning, for example, around 3 axes.

Structural elements made of composite material that are characterized by a high volume fraction of fibers and at the same time high specific mechanical properties, such as, for example, high strengths, can be made from fiber preforms made by the method of the invention. Therefore, the invention also relates to a method for manufacturing a structural element from a fibrous composite material using a fiber preform, which was manufactured by the inventive method for manufacturing a fiber preform, which includes the following steps:

- the input of the fibrous preform manufactured by the method of the invention into the forming device;

- applying pressure and / or vacuum and / or elevated temperature to the fiber preform to form a structural element from the fibrous composite material;

- cooling of a structural element of a fibrous composite material;

- removing the structural element from the fibrous composite material from the forming device.

Depending on the content of the matrix material present in the used fiber preform, as well as on the type of matrix material, various embodiments of the method of manufacturing a structural element from a composite material are obtained. Thus, a structural element made of composite material can be manufactured by the above steps of the method by direct pressing, without the need for additional matrix material, when the used fiber preform was manufactured in accordance with the invention using the prepreg method in the form of at least one bundle of reinforcing fibers equipped with a binder, and the prepreg had a matrix or corresponding binder content above about 25 weight. % It is also possible, for example, to manufacture a structural element from a composite material by direct pressing, if in the manufacture of a fiber preform, although ribbon-shaped strands of reinforcing fibers equipped with a binder were taken as the basis for which the concentration of the binder was relatively low and insufficient for the manufacture of the structural element with continuous matrix phase, however, before laying the fiber bundles, additional matrix material was supplied when laying the fiber bundles.

The pressing time under pressure and / or vacuum and at elevated temperature depends, in particular, on the type of matrix material. If the matrix material is a thermoplastic polymer or a mixture of thermoplastic polymers, the pressing times can be relatively short. For binders and / or matrix materials based on uncured or partially cured thermosetting polymers, the required pressing time depends on the time periods required to cure the matrix.

In the case when a fiber preform is used in the method of manufacturing a structural element from a composite material, in which the fiber bundles have only a relatively small binder content, for example, in the range from 2 to 14 weight. % relative to the binder reinforcing filament, and the binder, for example, is based on uncured or partially cured thermosetting polymers or resins, in accordance with the method mentioned above for infusion or injection of the matrix material, the matrix material additionally necessary for the manufacture of the structural element from the composite material can be introduced into the forming device, before then pressing occurs under pressure and / or vacuum and at elevated temperature to obtain const uktivnogo element.

To perform the method of the invention, a stacking device is best suited, which needs to be explained below with the help of a schematic diagram in FIG. one.

Proposed by the invention, the laying device must be explained below using schematic images in the drawings, which show:

FIG. 1: side view of a segment of a stacking device provided with a stacking head;

FIG. 2: isometric view of a segment of the stacking device of FIG. one;

FIG. 3: a stacking device equipped with an articulated robot.

In FIG. 1 shows a schematic illustration of a segment of a stacking device in which the stacking head 1 is connected to the controlled positioning unit 3 by a hinge 2. In this case, two feeders 4 for coils 5 are connected to the laying head 1 as means for providing ribbon-shaped tows 6 of reinforcing fibers provided with a binder, the drive of which is preferably carried out by means of servomotors. The connection between the laying head 1 and the feeders can be carried out by means of appropriate holders (not shown here).

From the coils 5 located on the feeders, the ribbon-shaped strands 6 of reinforcing fibers provided with a binder are unwound and guided around the spreader roller 7, which is preferably barrel-shaped. By means of a straightening roller 7, the strands 6 are straightened and, if necessary, are stretched in width. With a barrel-shaped design of the straightening roller 7, the lateral direction of the harnesses 6 can be simultaneously carried out.

From the straightening roller 7, the harnesses 6 are led to the first conveying device 8, which in the stacking device in FIG. 1 consists of a pair of drive rollers. In this case, the lower roller 9 is pressed by the tensioning device 10 against the upper roller 11 provided with a rubber coating, so that the transportation of the harnesses 6 can be carried out without slipping.

After passing through the first conveying device 8, the bundles 6 are led to a longitudinal separation device 12, in which the bundles 6 are cut in the direction of their length into a portion 13 of the bundles. To do this, a system of several rotating separation discs 14 is used, to which the shared harnesses 6 are pressed with a certain force by means of two pressure-controlled pressure rollers 15. The parts 13 of the harness obtained in the longitudinal separation device 12 are brought to the second conveying device also made as a pair of drive rollers 16. By setting the speed difference between the second conveying device 16 and the first conveying device 8, at which the transportation speed of the second of the transport device 16 is set slightly higher than the speed of the first transport device 8, a certain tension of the bundles 6 and the parts of the bundle 13 can be created, thereby obtaining an improved cutting result in the longitudinal separation device 12.

The lower roller 17 of the second conveying device 16 simultaneously serves as the counter roller of the transverse separation unit 18, made in the present example in the form of a rotary transverse cutter, including the knife roller 19 and the counter roller 17. In the transverse separation unit 18, the tow portions 13 are cut into bundles of reinforcing fibers or, respectively, bundles of 20 fibers with a certain length. The transversely divided bundles 20 of fibers are taken from the transverse separation unit by the nozzle head 21 and, via the nozzle channel of the nozzle head 21, into which compressed air is supplied, are sprayed onto the surface to produce a fiber preform at an increased speed.

In FIG. 2 to explain the spatial arrangement, in particular of the elements of the laying head, shown in FIG. 1, a segment of a stacking device is shown in perspective in the image, with the same reference signs in the drawings refer to the same elements of the device.

In FIG. 3 shows one embodiment of a method of the invention according to the invention, equipped with a robot 23 with an articulated arm located on the machine base 22, at the end of which a laying head 1 is mounted by a hinge 24, and by means of which the laying head can move along several axes relative to the surface 25 a shaped body used to make a fiber preform. In this case, the fiber bundles 20 obtained on the laying head 1 by means of the longitudinal separation device 12 and the transverse separation unit 18 and carried out through the nozzle head 21, are sprayed onto the surface 25 according to certain requirements according to the structure requirements of the manufactured fiber billet or correspondingly made structural element from composite material trajectories.

Claims (29)

1. A method of manufacturing a fiber preform by laying bundles of reinforcing fibers on the surface and / or on bundles of reinforcing fibers laid on the surface, comprising the steps of: - the supply of at least one endless ribbon-shaped tow of reinforcing fibers provided with a binder from the feeder to the laying head, said at least one tow having a tow width of at least 5 mm and a binder concentration in the range of 2 to 70 weight. % relative to the weight of the ribbon-shaped tow, - straightening said at least one endless ribbon-shaped tow in a spacer assembly located on the stacking head and transporting said at least one tow in the transport direction by means of the first transport device located on the stacking head to the longitudinal separation device located on the stacking head, - when stabilizing the specified at least one harness in the direction transverse to the direction of transportation, - cutting said at least one tow in a longitudinal separation device along its longitudinal extent by means of at least one dividing element into two or more parts of the tow, - transporting the parts of the tow in the transport direction by means of the second transport device located on the stacking head to the transverse separation unit located on the stacking head, - cutting the parts of the tow by means of a transverse separation unit into bundles of reinforcing fibers of a certain length, and - laying the bundles of reinforcing fibers on the surface and / or on the bundles of reinforcing fibers laid on the surface and fixing the bundles of reinforcing fibers on the surface and / or on the bundles of reinforcing fibers laid on the surface to form a fiber preform, while a relative movement is established between the laying head and the surface for laying bundles of reinforcing fibers on the surface, taking into account the load. 2. A method of manufacturing a fibrous preform according to claim 1, characterized in that said at least one bundle is a filament yarn having at least 12,000 filaments. 3. A method of manufacturing a fibrous preform according to claim 1 or 2, characterized in that said at least one strand is a pre-impregnated filament, and the binder consists of a composition of the first and second resin, wherein the filament of the filament is impregnated with the composition of the first resin and at least partially connected by means of this composition of the first resin, and this composition of the first resin contains at least two bisphenol A epichlorohydrin-resins H1 and H2 in a weight ratio of H1: H2 from 1.1 to 1.4, while H1 has an epo the acid number is from 1850 to 2400 mmol / kg, the average molecular weight M _{N is} from 800 to 1000 g / mol and is solid at room temperature, and H2 has an epoxy number from 5000 to 5600 mmol / kg, the average molecular weight M _N <700 g / mol and is liquid at room temperature, and, in addition, contains an aromatic polyhydroxy ester P1, which has an acid number of from 40 to 55 mg KOH / g and an average molecular weight M _{N of} from 4000 to 5000 g / mol, and pre-impregnated with it the filament on its outer side has a second resin composition in the form of adhering to fil cops particles or droplets, and this second resin composition is solid at room temperature, has a melting point in the range from 80 to 150 ° C and has a thread on an outer side in a concentration of from 0.5 to 10 wt. % relative to the total weight of the pre-impregnated filament yarn, and at least 50% of the outer side of the yarn is free of the second resin composition, and inside the yarn is free of the second resin composition. 4. A method of manufacturing a fiber preform according to claim 2, characterized in that the binder is present in a concentration in the range from 2 to 14 weight. % relative to the total weight of the binder filament. 5. A method of manufacturing a fiber preform according to claim 1, characterized in that said at least one strand is a prepreg having reinforcing fibers unidirectionally arranged in the direction of the length of the bundle. 6. A method of manufacturing a fiber preform according to claim 5, characterized in that the binder is present in a concentration ranging from 15 to 70 weight. % relative to the unit area of the weight of the prepreg. 7. A method of manufacturing a fiber preform according to claim 1, characterized in that said at least one tow in the longitudinal separation device is cut into more than two parts of the tow. 8. A method of manufacturing a fiber preform according to claim 1, characterized in that said at least one strand has a width to thickness ratio of at least 20. 9. A method of manufacturing a fiber preform according to claim 1, characterized in that the width of the parts of the tow is in the range from 0.5 to 5 mm. 10. A method of manufacturing a fiber preform according to claim 1, characterized in that the bundles of fibers cut by means of a transverse separation unit have a length ranging from 10 to 100 mm. 11. A method of manufacturing a fibrous preform according to claim 1, characterized in that several plaits of reinforcing fibers provided with a binder, lead to the laying head, and these several plaits can be the same or different. 12. A method of manufacturing a fiber preform according to claim 1, characterized in that the laying head is connected to an adjustable positioning unit, by which the laying head moves relative to the surface. 13. A method of manufacturing a fibrous preform according to claim 1, characterized in that the bundles of fibers after the transverse separation unit and before laying on the surface and / or on the bundles of reinforcing fibers laid on the surface are heated. 14. A method of manufacturing a fibrous preform according to claim 1, characterized in that the fiber bundles through the nozzle channel of the nozzle head into which compressed air is supplied are diverted from the transverse separation unit. 15. A method of manufacturing a fiber preform according to claim 1, characterized in that, together with the fiber bundles, a matrix material in the form of particles or droplets is sprayed onto the surface and / or on the surface-reinforced fiber bundles. 16. A method of manufacturing a fiber preform according to claim 15, characterized in that a matrix material in the form of particles is introduced into the nozzle channel, which, together with bundles of fibers, is sprayed onto the surface and / or bundles of reinforcing fibers laid on the surface. 17. A method of manufacturing a fiber preform according to claim 1, characterized in that the step of laying the bundles of reinforcing fibers is followed by a compacting step in which the stacked bundles of reinforcing fibers are compacted to achieve a higher volume fraction of fibers. 18. A method of manufacturing a structural element from a fibrous composite material using a fiber preform made according to one or more of claims. 1-17, comprising the steps of: - input of the fibrous preform into the forming device; - applying pressure or vacuum and / or elevated temperature to the fiber preform to form a structural member from the fibrous composite material; - cooling of a structural element of a fibrous composite material; - removing the structural element from the fibrous composite material from the forming device.

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